A method of manufacturing a gear is disclosed in JP9(1997)-308934A. Disclosed in JP9(1997)-308934A is a method of forming a tooth surface by rolling after a tooth shape is roughly formed from a blank by cutting.
In a case where the tooth surface of the gear is formed by rolling, a load applied to the tooth surface when rolling changes in response to a change in engagement between the tooth surface and a rolling die. When the changes in the load become great, changes in surface pressure applied to the roughly shaped tooth during a deformation processing also become greater. Accordingly, waviness (unevenness) may be formed on the tooth surface. In a helical gear, once a gear specification, a size of a face width and the like are determined, the changes in the engagement between the tooth surface and the rolling die are automatically determined. In order to control a level of the changes in the engagement, the gear specification, such as a width of a gear and the like, the face width and the like need to be changed, which may result it significant design change. For example, an increase of the width of the gear may cause disadvantage in weight and costs. On the other hand, a decrease of the width of the gear may cause difficulties in ensuring a necessary strength of the gear.
A need thus exists to provide a helical gear and a method of manufacturing the same which are not susceptible to the drawback mentioned above.